1. Field of the Application
The present invention relates to electrothermics and in particular to assemblies for induction heating generally known as induction heaters.
The invention is intended for use in induction melting and heating installations.
2. Description of the Prior Art
There is known a wide variety of induction heaters (cf. "Induction Melting Furnaces", by A. M. Vineberg, Moscoe Publishers, 1967, pp. 310-315, /in Russian/, which basically comprise an induction coil, a system for its cooling, and heat insulation. To achieve maximum efficiency in the use of power, the induction coil is formed of metals having low specific resistance, such as aluminum and copper; and to accomplish a maximum power per unit area, i.e. to increase the current of the induction coil, an air- or water cooling system is used. Heat insulation is utilized to reduce heat losses which occur at the surface of the heated metal.
The prior-art devices of the type described above, when operated at frequencies of 50 to 60 Hz, have the following power characteristics: power efficiency is 60 to 80 percent, power per unit area being not more than 1000 kW/m.sup.2. In conventional induction heating and melting furnaces utilizing power capacity of 5 to 30 MW and above, the power losses in the induction coil are estimated at 1 to 10 MW, such value of the power per unit area being the reason for their insufficiently high production capacity.
There is also known an induction heater (cf. USSR Inventor's Certificate No. 193,631), which comprises an induction coil provided with a cooling system, a heat-insulating element in the form of a ceramic crucible, and a water-cooled metal baffle interposed therebetween.
However, the employment of the water-cooling system fails to accomplish power characteristics superior to those indicated above. It should be observed that the cooled baffle installed in the given device is used to facilitate the operation of the heat-insulating element under the prevailing heat conditions. With this purpose in view, a cooled baffle is positioned immediately adjacent to the heat-insulating element, which is the ceramic crucible in the given case.